Zero-configuration bundler for tiny JS libs, powered by Rollup.

Usage no npm install needed!

<script type="module">
  import codewitchbellaMicrobundle from 'https://cdn.skypack.dev/@codewitchbella/microbundle';



Microbundle npm travis

The zero-configuration bundler for tiny modules, powered by Rollup.

✨ Features:

  • One dependency to bundle your library using only a package.json
  • Support for ESnext & async/await (via Bublé & async-to-promises)
  • Produces tiny, optimized code for all inputs
  • Supports multiple entry modules (cli.js + index.js, etc)
  • Creates multiple output formats for each entry (CJS, UMD & ESM)
  • 0 configuration TypeScript support
  • Built-in Terser compression & gzipped bundle size tracking

🔧 Installation


npm i -D microbundle

Set up your package.json

  "source": "src/foo.js",         // Your source file (same as 1st arg to microbundle)
  "main": "dist/foo.js",        // output path for CommonJS/Node
  "module": "dist/foo.mjs",     // output path for JS Modules
  "unpkg": "dist/foo.umd.js",   // optional, for unpkg.com
  "scripts": {
    "build": "microbundle",       // uses "source" and "main" as input and output paths by default
    "dev": "microbundle watch"

📦 Usage

Microbundle includes two commands - build (the default) and watch. Neither require any options, but you can tailor things to suit your needs a bit if you like.

microbundle / microbundle build

Unless overridden via the command line, microbundle uses the source property in your package.json to locate the input file, and the main property for the output.

For UMD builds, microbundle will use a snake case version of the name field in your package.json as export name. This can be overridden either by providing an amdName key in your package.json or via the --name flag in the cli.

microbundle watch

Acts just like microbundle build, but watches your source files and rebuilds on any change.

Using with TypeScript

Just point the input to a .ts file through either the cli or the source key in your package.json and you’re done.

Specifying builds in package.json

You can specify output builds in a package.json as follows:

"main": "dist/foo.js",          // CJS bundle
"umd:main": "dist/foo.umd.js",  // UMD bundle
"module": "dist/foo.mjs",       // ES Modules bundle
"source": "src/foo.js",         // custom entry module (same as 1st arg to microbundle)
"types": "dist/foo.d.ts",       // TypeScript typings

Mangling Properties

Libraries often wish to rename internal object properties or class members to smaller names - transforming this._internalIdValue to this._i. Microbundle doesn't currently do this by default, but it can be enabled by adding a "mangle" property to your package.json, with a pattern to control when properties should be mangled. To mangle all property names beginning an underscore, add the following:

    "mangle": {
        "regex": "^_"

All CLI Options

    $ microbundle <command> [options]

  Available Commands
    build    Build once and exit
    watch    Rebuilds on any change

  For more info, run any command with the `--help` flag
    $ microbundle build --help
    $ microbundle watch --help

    -v, --version    Displays current version
    -i, --entry      Entry module(s)
    -o, --output     Directory to place build files into
    -f, --format     Only build specified formats  (default es,cjs,umd)
    -w, --watch      Rebuilds on any change  (default false)
    --target         Specify your target environment (node or web, default web)
    --external       Specify external dependencies, or 'none'
    --globals        Specify globals dependencies, or 'none'
    --define         Replace constants with hard-coded values
    --alias          Map imports to different modules
    --compress       Compress output using Terser  (default true)
    --strict         Enforce undefined global context and add "use strict"
    --name           Specify name exposed in UMD builds
    --cwd            Use an alternative working directory  (default .)
    --sourcemap      Generate source map  (default true)
    --raw            Show raw byte size  (default false)
    --jsx            A custom JSX pragma like React.createElement (default: h)
    -h, --help       Displays this message

    $ microbundle microbundle --globals react=React,jquery=$
    $ microbundle microbundle --define API_KEY=1234
    $ microbundle microbundle --alias react=preact
    $ microbundle microbundle --no-sourcemap # don't generate sourcemaps

🛣 Roadmap

Here's what's coming up for Microbundle:

🔨 Built with Microbundle

🥂 License